Re: [PATCH v3 1/9] string: introduce memweight
2012/6/21 Tony Luck tony.l...@gmail.com: On Fri, Jun 8, 2012 at 5:50 PM, Akinobu Mita akinobu.m...@gmail.com wrote: lib/string.c | 36 Is lib/string.c the right place for this? I get a build error on the ia64 sim_defconfig: LD arch/ia64/hp/sim/boot/bootloader It fails because it pulls in lib/lib.a(string.o) to get some innocuous function like strcpy() ... but it also gets given memweight() which relies on __bitmap_weight() which it doesn't have, because it doesn't include lib/built-in.o (which is where bitmap.o, the definer of __bitmap_weight(), has been linked). Moving memweight() to lib/bitmap.c fixes the problem. But it isn't really clear that it belongs there either. Perhaps it should be its own file lib/memweight.c that gets included in lib/lib.a? I'll fix it by making lib/memweight.c as you suggested. Thanks for your report and suggestion. -- To unsubscribe from this list: send the line unsubscribe linux-media in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
Re: [PATCH v3 1/9] string: introduce memweight
On Fri, Jun 8, 2012 at 5:50 PM, Akinobu Mita akinobu.m...@gmail.com wrote: lib/string.c | 36 Is lib/string.c the right place for this? I get a build error on the ia64 sim_defconfig: LD arch/ia64/hp/sim/boot/bootloader It fails because it pulls in lib/lib.a(string.o) to get some innocuous function like strcpy() ... but it also gets given memweight() which relies on __bitmap_weight() which it doesn't have, because it doesn't include lib/built-in.o (which is where bitmap.o, the definer of __bitmap_weight(), has been linked). Moving memweight() to lib/bitmap.c fixes the problem. But it isn't really clear that it belongs there either. Perhaps it should be its own file lib/memweight.c that gets included in lib/lib.a? -Tony -- To unsubscribe from this list: send the line unsubscribe linux-media in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
Re: [PATCH v3 1/9] string: introduce memweight
On Sat, 9 Jun 2012 09:50:30 +0900
Akinobu Mita akinobu.m...@gmail.com wrote:
memweight() is the function that counts the total number of bits set
in memory area. Unlike bitmap_weight(), memweight() takes pointer
and size in bytes to specify a memory area which does not need to be
aligned to long-word boundary.
...
+/**
+ * memweight - count the total number of bits set in memory area
+ * @ptr: pointer to the start of the area
+ * @bytes: the size of the area
+ */
+size_t memweight(const void *ptr, size_t bytes)
+{
+ size_t w = 0;
Calling the return value ret is a useful convention and fits well here.
+ size_t longs;
+ const unsigned char *bitmap = ptr;
+
+ for (; bytes 0 ((unsigned long)bitmap) % sizeof(long);
+ bytes--, bitmap++)
+ w += hweight8(*bitmap);
+
+ longs = bytes / sizeof(long);
+ if (longs) {
+ BUG_ON(longs = INT_MAX / BITS_PER_LONG);
+ w += bitmap_weight((unsigned long *)bitmap,
+ longs * BITS_PER_LONG);
+ bytes -= longs * sizeof(long);
+ bitmap += longs * sizeof(long);
+ }
+ /*
+ * The reason that this last loop is distinct from the preceding
+ * bitmap_weight() call is to compute 1-bits in the last region smaller
+ * than sizeof(long) properly on big-endian systems.
+ */
+ for (; bytes 0; bytes--, bitmap++)
+ w += hweight8(*bitmap);
+
+ return w;
+}
+EXPORT_SYMBOL(memweight);
diff -puN lib/string.c~string-introduce-memweight-fix lib/string.c
--- a/lib/string.c~string-introduce-memweight-fix
+++ a/lib/string.c
@@ -833,18 +833,18 @@ EXPORT_SYMBOL(memchr_inv);
*/
size_t memweight(const void *ptr, size_t bytes)
{
- size_t w = 0;
+ size_t ret = 0;
size_t longs;
const unsigned char *bitmap = ptr;
for (; bytes 0 ((unsigned long)bitmap) % sizeof(long);
bytes--, bitmap++)
- w += hweight8(*bitmap);
+ ret += hweight8(*bitmap);
longs = bytes / sizeof(long);
if (longs) {
BUG_ON(longs = INT_MAX / BITS_PER_LONG);
- w += bitmap_weight((unsigned long *)bitmap,
+ ret += bitmap_weight((unsigned long *)bitmap,
longs * BITS_PER_LONG);
bytes -= longs * sizeof(long);
bitmap += longs * sizeof(long);
@@ -855,8 +855,8 @@ size_t memweight(const void *ptr, size_t
* than sizeof(long) properly on big-endian systems.
*/
for (; bytes 0; bytes--, bitmap++)
- w += hweight8(*bitmap);
+ ret += hweight8(*bitmap);
- return w;
+ return ret;
}
EXPORT_SYMBOL(memweight);
_
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[PATCH v3 1/9] string: introduce memweight
memweight() is the function that counts the total number of bits set
in memory area. Unlike bitmap_weight(), memweight() takes pointer
and size in bytes to specify a memory area which does not need to be
aligned to long-word boundary.
Signed-off-by: Akinobu Mita akinobu.m...@gmail.com
Cc: Anders Larsen a...@alarsen.net
Cc: Alasdair Kergon a...@redhat.com
Cc: dm-de...@redhat.com
Cc: linux-fsde...@vger.kernel.org
Cc: Laurent Pinchart laurent.pinch...@ideasonboard.com
Cc: linux-media@vger.kernel.org
Cc: Mark Fasheh mfas...@suse.com
Cc: Joel Becker jl...@evilplan.org
Cc: ocfs2-de...@oss.oracle.com
Cc: Jan Kara j...@suse.cz
Cc: linux-e...@vger.kernel.org
Cc: Andrew Morton a...@linux-foundation.org
Cc: Andreas Dilger adilger.ker...@dilger.ca
Cc: Theodore Ts'o ty...@mit.edu
Cc: Matthew Wilcox matt...@wil.cx
---
v3: add comment for the last loop, adviced by Jan Kara
v2: simplify memweight(), adviced by Jan Kara
include/linux/string.h |3 +++
lib/string.c | 36
2 files changed, 39 insertions(+), 0 deletions(-)
diff --git a/include/linux/string.h b/include/linux/string.h
index e033564..ffe0442 100644
--- a/include/linux/string.h
+++ b/include/linux/string.h
@@ -145,4 +145,7 @@ static inline bool strstarts(const char *str, const char
*prefix)
return strncmp(str, prefix, strlen(prefix)) == 0;
}
#endif
+
+extern size_t memweight(const void *ptr, size_t bytes);
+
#endif /* _LINUX_STRING_H_ */
diff --git a/lib/string.c b/lib/string.c
index e5878de..e467186 100644
--- a/lib/string.c
+++ b/lib/string.c
@@ -26,6 +26,7 @@
#include linux/export.h
#include linux/bug.h
#include linux/errno.h
+#include linux/bitmap.h
#ifndef __HAVE_ARCH_STRNICMP
/**
@@ -824,3 +825,38 @@ void *memchr_inv(const void *start, int c, size_t bytes)
return check_bytes8(start, value, bytes % 8);
}
EXPORT_SYMBOL(memchr_inv);
+
+/**
+ * memweight - count the total number of bits set in memory area
+ * @ptr: pointer to the start of the area
+ * @bytes: the size of the area
+ */
+size_t memweight(const void *ptr, size_t bytes)
+{
+ size_t w = 0;
+ size_t longs;
+ const unsigned char *bitmap = ptr;
+
+ for (; bytes 0 ((unsigned long)bitmap) % sizeof(long);
+ bytes--, bitmap++)
+ w += hweight8(*bitmap);
+
+ longs = bytes / sizeof(long);
+ if (longs) {
+ BUG_ON(longs = INT_MAX / BITS_PER_LONG);
+ w += bitmap_weight((unsigned long *)bitmap,
+ longs * BITS_PER_LONG);
+ bytes -= longs * sizeof(long);
+ bitmap += longs * sizeof(long);
+ }
+ /*
+* The reason that this last loop is distinct from the preceding
+* bitmap_weight() call is to compute 1-bits in the last region smaller
+* than sizeof(long) properly on big-endian systems.
+*/
+ for (; bytes 0; bytes--, bitmap++)
+ w += hweight8(*bitmap);
+
+ return w;
+}
+EXPORT_SYMBOL(memweight);
--
1.7.7.6
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